1. Field of the Invention
The present invention relates to a method of dyeing a synthetic fiber material and a dyed synthetic fiber material.
More particularly, the present invention relates to a method of dyeing a synthetic fiber material with an organic coloring material at a high temperature to produce deeply and evenly colored synthetic fiber material having a significantly enhanced color fastness, and a dyed synthetic fiber material.
2. Description of the Related Art
It is well known that synthetic fiber materials, for example, fabrics, are employed not only for various types of clothes but also for various types of industrial materials. Almost all of the synthetic fiber materials are colored. Also, a major portion of the colored synthetic fiber materials are produced by a dyeing method using a dye, whereas a minor portion of the colored synthetic fiber materials are produced by a printing method or dope-coloring method in which a pigment is mixed with a synthetic polymer material.
Recently, various fabrics are produced from combined filament yarns containing extremely fine synthetic fibers or two or more types of synthetic fibers different in dyeing property from each other, and become widely employed in various uses. Accordingly, there is a strong demand for developing a new method of dyeing the synthetic fiber materials at a high color depth and at a high evenness.
For example, the extremely fine fibers have a large total surface area per unit weight of the fibers, and thus light irradiated on the extremely fine fibers is reflected on a large total surface area. Therefore, when the same amount of dye is adsorbed in the fibers, the color depth of the dyed extremely fine fibers appears lower than that of fibers having a higher diameter than that of the extremely fine fibers. Accordingly, various methods for dyeing the extremely fine fibers at a high color depth are developed.
In the most simple method, the amount of dye to be applied to the fibers is increased so as to increase the amount of the dye to be adsorbed by the fibers. This method is, however, disadvantageous in that the dyeing cost becomes high, and in the dyed fibers, an increase in the amount of the dye adsorbed in the fibers causes the amount of the dye desorbed from the dyed fibers to be increased, in other words, the increase in the absorbed dye amount results in a reduction in washing fastness of the dyed fibers.
It is known that hydrophilic synthetic fibers having a high crystallinity, for example, polyester fibers, can be dyed with a water-insoluble disperse dye by a carrier dying method in which an additive, for example, acetophenone or o-phenylphenol, is used as a carrier. This carrier dyeing method is, however, disadvantageous in that the removal of the carrier from the dyed fibers is difficult, the dyed fibers are deteriorated by the carrier, the waste water containing the carrier has a bad odor and is harmful to the environment, and the treatment of the waste water is difficult.
To eliminate the above-mentioned disadvantages, Japanese Unexamined Patent Publication (Kokai) No. 59-71,487 discloses a method of dyeing a false-twisted yarn of a cationic dye-dyeable polyester filaments with a cationic dye at a temperature of 120.degree. C. or more. This method is characterized only in that the cationic dye having higher wet color fastness and sublimation color fastness than those of disperse dye is used to prevent a reduction in color fastness of a dyed filament yarn material after a resin treatment is applied thereto. Therefore, when the dyeing method is applied to the extremely fine fiber material, it is impossible to obtain both the high dyeability (color depth) and the high washing fastness of the dyed fiber material.
Further, when a composite yarn material comprising two or more types of fibers different in dyeability are dyed, the different types of fibers are dyed with the dye at different dyeing rates from each other, and thus the dyed fibers are different in hue and color depth from each other. The resultant dyed composite yarn material exhibits a melange (sprinkly) colored appearance.